An evaluation of spontaneous adverse drug reaction monitoring systems.

The Food and Drug Administration maintains an adverse drug reaction reporting system. Physicians report suspected adverse reactions that occur while a patient is taking a drug; reporting is voluntary and spontaneous. Data from spontaneous adverse drug reaction reporting systems are designed to signal that rare, unsuspected adverse reactions exist as a result of using a specific drug. Problems arise when attempts are made to use such data for other purposes. Specifically, spontaneous adverse drug reaction data, such as those published by the Food and Drug Administration, are inappropriate for calculating actual adverse drug reaction rates for specific drugs or for making safety comparisons among drugs. This is because these data are subject to numerous biases that can be easily identified and described but not easily corrected. As a result, data from spontaneous adverse drug reaction reporting systems bear little relationship to the actual incidence of adverse drug reactions.